Production of seamless tubes



, y 1934. R. c. STIEFEL' 1,957,915

PRODUCTION OF SEAMLESS TUBES Filed July 27, 1932 Patented May 8, 1934 PATENT OFFICE UNITED STATES Claims.

The invention relates to the manufacture of seamless metallic tubes by means of cross-rolls, and it comprises certain improvements and modifications both in the apparatus and in the method 5 described and claimed in my co-pending application for Letters Patent, Serial No. 625,040, filed July 27, 1932.

As is'stated in my other said application, it is well known that the crossrolling of a metal billet or blank on a mandrel tends to enlarge or expand the blank laterally or circumferentially of the mandrel, and that such lateral expansion or circumferential flow of metal greatly retards and interferes with the desired elongation of the blank in tubular form. Such tendency toward lateral expansi on of the billet may be briefly explained as follows: The well-known action of cross-rolls is to draw the metal of a. billet into the wall-reducing pass formed between the crossrolls and the mandrel. The metal of the billet is in contact with the roll faces in the interval between the point where the metal enters the pass and the point where it leaves the pass. For purposes of explanation, the longitudinal feeding speed of the cross-rolls may be considered constantthroughout this interval in which the rolls engage the metal of the billet. That is tosay, the tendency of the rolls to feed the billet longitudinally may be considered substantially the same at, all points of contact between the rolls and the billet. Accordingly, per unit of time, the rolls tend to feed from the'pass a length of billet substantially equal to the length drawn into the pass. Since, however, wall reduction 01' the billet is effected in the pass, it will be under stood that the cross-sectional area of the billetwall is greater at the entering end of the pass than at the leaving end, and, longitudinal feed being substantially equal at all points in the pass, the tendency of the rolls is to feed a greater volume of metal into the pass than leaves the pass. Inasmuch as the rolls tend to feed into the pass a volume of metal greater than the volume delivered from the pass, there is a resulting surplus volume of metal, tending to flow laterally or circumferentially of the mandrel and cause an enlargement or distortion of the blank or tube.

Unless cross-sectional enlargement of the hollow blank or billet is desired, the flow or displacement of metal should be practically all in the general direction of tube generation. In brief, the object of this invention, as well as the invention defined in my above-noted patent application, is to minimize the so-called lateral flow of 55 metal, and to promote in greater measure the end in a carriage 4; the carriage 4 is movable flow of metal more nearly along lines parallel to the axis of tube generation. In other words, I seek to provide for maximum elongation of the billet per unit of wall reduction. v

I attain the objects of this invention by restraining or limiting the volume of metal enter-' ing the cross-rolling pass, and I limit such entering volume of metal by means of a retreating detent acting upon the billet. Advantageously, the detent comprises the mandrel upon which the billet is rolled.

By the term cross-rolls in this specification, and in the appended claims, I intend to include disk rolls and any other oblique acting rolls, which in operating upon a billet tend to produce both the rotation and longitudinal movement thereof.

In the accompanying drawing there is shown diagrammatically apparatus for the practice of the invention. Figure 1 is a general view of such apparatus, partly in plan and partly in medial horizontal section; and Figures 2 and 3 are fragmentary views in cross-section taken, respectively, on the planes II-II and III-'III of Figure 1.

The reference numeral 1 is applied to a mandrel upon which a specially prepared billet B is placed and subjected to the action of a pair of cross-rolls 2 and 3. For reasons presently to appear, the billet B is made initially of hollow 85 cylindrical form and is closed at its one end, the left-hand end in Figure 1.

The mandrel 1 is supported at its right-hand along a bed 5, and its movement is controlled by means of a pneumatic cylinder 6. The piston of cylinder 6 is connected to carriage 4 by rod '7. The mandrel 1 is free to rotate in its supporting carriage 4, and the action of theopposed cross-rolls upon the billet tends to produce both rotation and axial movement of the mandrel. The left-hand end of the mandrel 1 abuts against the external end wall of the billet B, and as stated, the action of the cross-rolls upon the billet tends to produce rotation and a left-to-right movement or retreat of the mandrel. The axial movementor retreat of the mandrel 1 is retarded to a speed less than the speed of the rolls which is normally effective at the entrance of the pass to produce longitudinal flow of metal, and thereby the volume of metal entering the roll pass is restrained or limited. Thus by regulating the retreat of the mandrel during wall reduction of the billet, metal flow will be accomplished to the desired extent along lines generally parallel to the axis of tube generation.

It is evident that the invention can be practiced in roll passes which include more than two cross-rolls, it being only for purposes of illustrationthat I have shown a common two-roll arrangement 2, 3 with the usual stationary guides 10, 10. In the illustration I have shown a pneumatic cylinder 6 as the means for controlling the retreat of the mandrel and its travelling support 4. The cylinder 6 is provided with a valved vent 8, so that a controlled escape of air regulates the retreating speed of the mandrel. I contemplate, however, that positive mechanical, hydraulic, or electrical means, within the knowledge of the engineer, may be used in place of or in combination with the pneumatic cylinder 6.

An advantage of particular merit is realized in the invention. It will be perceived that the mandrel 1, in retarding the feed of metal under the pull of the cross-rolls, causes the metal to be subjected to tension.

While in methods employed hitherto the metal blank has been subjected to tension during rolling, such tension was produced by a second or third pass of cross-rolls pulling the blank fromthe first pass. Of course, the two roll passes necessarily are arranged at an interval from one another, and manifestly regions at each end of the tube or blank, equal to the interval between these two passes, are not subjected to this tension. Ac-

cordingly, the tube is not subjected to uniform, metal-working action throughout the length of the tube, and as a result the physical characteristics of the product are not precisely uniform at all points in its length.

Upon considering my invention it will be obvious that one pass of rolls may be employed, and the tension upon the metal blank may be obtained in such pass, by reason of the retarded travel of the mandrel. It will further be observed that the tension may be produced at the instant the entering end of the blank is drawn into the pass, and that such tension may be uniformly maintained throughout the working of the entire length of the blank. Thus greater uniformity in product is obtained.

I claim as my invention:

1. The method of manufacturing a metal tube which comprises effecting the entrance of the leading end of a metal blank upon a mandrel into a single or primary metal-working pass and subjecting the metal of the blank to the feeding action of a plurality of cooperating rolls, maintaining positive engagement between said mandrel and the trailing end of said blank, causing the progressive retreat of the mandrel in the direction and on the line of feed of said rolls.

regulating the speed of retreat of said mandrel -to a value below the feeding speed of said rolls,

thereby maintaining the blank throughout its length from its trailing end to said pass under tension, and thereby restraining the entrance of and longitudinal feeding action of a single or primary pass formed by a set of cross-rolls, retarding the retreat of the mandrel to a speed below the feeding speed of said rolls,thereby, by frictional engagement between the blank and the face of said mandrel, retarding the feeding of metal into said pass, and subjecting the blank to tension while advancing into said single or primary pass by maintaining positive engagement ,between the mandrel and the trailing end of the blank, and thereby restraining the advance of metal into said single or primary pass to a speed below the feeding speed of the rolls as retarded by said frictional engagement between the blank and the face of the mandrel.

3. The method of rolling a metal blank to form a tube, comprising progressively subjecting the blank while on a retreating mandrel to the re ducing and longitudinal feeding action of a single or primary pass formed by a set of cooperating rolls, retarding the retreat of the mandrel to a speed below the feeding speed of said rolls. and throughout progress of the blank through the pass subjecting the blank to tension while it is advancing into said single or primary pass by applying positive restraint upon the trailing end of the blank, and thereby restraining the advance of metal .into said pass to a speed below the feeding speed which the joint action of said rolls=-and mandrel otherwise tends to effect.

4. The method of rolling a metal blank to form a tube, comprising progressively subjecting the blank while on a mandrel to the reducing and longitudinal feeding action of a single or primary pass formed by a set of cooperating rolls. subjecting the metal being worked to tension by causing said rolls to feed the metal against the restraint imposed by frictional engagement between the blank and the mandrel'within said pass, and applying restraint upon the trailing end of the blank, and thereby subjecting to tension the metal between such trailing end and the entrance to said pass, whereby the advance of metal into said pass is restrained to a speed below the-feeding speed of said rolls as restrained by said mandrel.

5. The method of producing a seamless tube.

drel at less velocity than the feeding speed of rolls and thereby exerting tension on the metal in said pass, and exerting a second tension upon the metal in or adjacent said pass bythe action of rolling or guide means, and, at a point before the entrance to said single or primary pass, applying restraint upon the trailing end of the blank, thereby subjecting to tension the metal between such trailing end and the entrance to said pass, whereby the metal being worked in said single or primary pass is subject to at least three tension eifects.

' RALPH C. STIEFEL. 

